Extensible ladder



March 5, 1946. M. E. BAKER EXTENSIBLE LADDER Filed Jan. 12, 1945 2 Sheets-Sheet 1 lNV ENTOR MELYN E, BAKER ATTORNEY March 5, 1946.

M. E. BAKER EXTENSIBLE LADDER Filed Jan. 12, 1945 2 Sheets-Sheet 2 INVENTOR.

M ELYN E. BAKER ATTORNEY Patented Mar. 5, 1946 UNITED STATES PATENT OFFICE EXTENSIBLE LADDER Melyn E. Baker, Portland, Or'eg. Application January 12, 1945, Serial No. 572,519

Claims. 7 (Cl. 228--19.2)

This invention relates to an extensible ladder that employs a novel application of the principle of a lazy-tongs, a system of jointed bars capable'of great extension. Originally such a device was for picking up something without stoopzero stability in the other direction unless the bars are made quite wide and therefore heavy and even then. too small for more than limited use-v fulness. It is, therefore, another object to greatly'stiffen the extensible ladder made after and employing a modified lazy-tongs system, by

making the bars in a double column and adding horizontal bars.

The foregoing and other objects that will be apparent, constitute the purposes of this invention.

Drawings illustrating it in its best. form, as now known, accompany and form apart of the disclosure herein, showing its application to a rescue ladder for use in safely removing persons trapped above a conflagration in hotels, lodging houses, apartments and like structures.

Ordinary extension ladders will often have to extend upwards through flame belching windows, hence are unusable. Extension ladders mounted on a truck are in common use, but are limited to the rescue of at most three persons at a time, by getting on and backing the truck. So I have illustrated my invention as applied to and constructed for that purpose; but as stated, it is not so limited and the novel structural features can, of course, be devoted to any useful purpose.

In the drawings: Fig. 1 shows the invention in perspective, with that serve as rungs of a 4 and swingable with respect to the shank by virture of a plural set of hinges;

Fig. 3 is a fragmentary view' of an extension ladder according to the invention, being part of a section of Fig. 4, on the line 33, Fig. 4;

Fig. 4 is a section of Fig. 3 on the line 4--4, Fig. 3; V

Fig. 5 is an enlarged view of the joint indicated by numeral 9 in Figs. 3 and 4, being the end pivotal joint of the double lazy-tongs system of jointed bars; and

Fig. 6 is an enlarged view of the hinged joint, numeral 6, of which one is used at every contact point of the shank and cross of the T formation.

Further describing the drawings; as will be seen at once from Figs. 1 and 2, the lazy-tongs principle is modified by being made double laterally. *This reduces the amount of extensibility to that of a single lazy-tong structure having a bar length of approximately one-half that used here; but the stability is so greatly enhanced that it is well Worth while. These bars I, are all counterparts of each other and at every inside intersection are joined by a pivot connection 2. Only a few of the bars are so designated and a less. number of joints bear the numeral 2, but the lazy-tongs principle is so old that further numerals are deemed unessential. The terminal-pivots bear numeral 9 as noted supra.

The double lazy-tongs shown in Fig. 3, is greatly, strengthened in every direction by the horizontal bars 4, which can be made straight the center part broken away to avoid repetition,

mounted on the rear end of a fiat bodied truck.

The top part shows the loading platform and the faced to serve as rungs of a ladder when extended in the manner shown in Fig. 1, lower part, or in suggested, they will be much stronger if made.

double as shown, with the lazy-tongs base between their two parts, but when made of wood for ordinary uses, nothing is thought gained by the double construction that will compensate the extra cost. It is an inescapable fact, however, that extreme extension can place the bars 4, so far apart that only a very active person could use them as a ladder.

A most important element of stability is the hinge 6, previously mentioned, which ties the cross X, and the shank of the T formations together without interfering'with their extensibilg l l ity. This hinged connection increases the strength of the extended structure many times, makes possible a platform l0, which will be anchored to the shank S, and the hinge 6, but notto the cross X, though it can rest on top of the topmost horizontal bar 4, as shown in the upper part of Fig. 1.

The truck in outline, at the bottom of Fig. 1, has a platform 12, and the shank portion of the ladder, designated by S, is securely fastened to it at I4. The other part or cross X, will be pivoted at I5, coaxially with the row of hinges 6, and bearing plates l6, diagrammatically indicate that it is swingable. That is to provide for backing the truck angularly when configurations of a building or obstructions make it expedient. A hydraulic cylinder 20 diagrammatically indicates a preferred means for making the ladder extensible, because however heavily loaded, it can then be lowered easily and smoothly. The hydraulic cylinder also serves to apply a hydraulic lock in-any position.

This invention can be made to operate at its best by constructing as much of it as possible, particularly the bars of both kinds, of the aluminum alloys that are light, strong and will stand a high temperature for a reasonable time without weakening or distorting.

Having illustrated and described my invention so that those familiar with the art to which it appertains may make and use it, what I claim as new and desire to secure by Letters Patent, is:

1. An extensible ladder comprising a lazy-tong system of pivotally connected jointed bars, there being two sets of bars hinge connected by the hinges between the ends of one set and the center portion of the other set, at least one set of the lazy-tong bars bearing horizontal bars for steps of a ladder pivotally connected to the central set of lazy-tong pivots and slot connected to the lateral terminal pivots of the lazy-tong bars.

2. An extensible ladder comprising a lazy-tong system of pivotally connected extensible jointed bars according to the lazy-tong principle, there being two sets of bars connected so that one set is normal to and jointed in T formation to the other, at least one set of the lazy-tong bars bearing horizontal bars for steps of a ladder pivotally connectedto the central set of lazy-tong pivots and slot connected to the lateral terminal pivots of the lazy-tong bars.

3. An extensible ladder comprising a lazy-tongs system of pivotally connected extensible jointed bars, the lazy-tongs being made double, laterally, there being two sets of lazy-tong bars hinge connected in T formation so that one set is normal to the other when the hinges are in median position, each pair of extensible lazy-tong bars bearing a horizontal bar pivotally connected to its center and slidably engaged with a pair of terminal pivotal connections that raise and lower concurrently with the center.

4. An extensible ladder comprising two sets of double lazy-tong bars jointedly connected vtogether in T formation to mutually stabilize each other, each pair of bars of the lazy-tong system of bars being pivotally connectedto a horizontal bar by its central pivot and slidably engaged with a terminal pivot of said double system of bars, to maintain horizontal relationship with said central pivot.

5. An extensible, collapsible structure for a ladder comprising two sets of double lazy-tong bars pivotally arranged, each set being a counterpart of the other set, the ends of one set connected to the center of the other set, said sets arranged to be concurrently raised and lowered in vertical planes at a substantial angle to each other so that the sets mutually support each other, each pair of bars of the lazy-tong system of bars in at least one set of double bars being pivotally connected to a horizontal bar with said horizontal bar slidably connected to a terminal lateral pivot of the said double system of bars.

MELYN E. BAKER. 

